1. Field of the Invention
The present invention relates to dot-matrix printing apparatus for generating characters or graphic patterns, and more particularly to such apparatus having a print head which is moved along the recording medium on a line-by-line basis.
2. The Prior Art
With the increasing need for universal character layout, which is capable of printing in different fields, printing bar codes, graphics, etc., printers are more frequently being designed as dot-matrix printers. In contrast to printers having fixed type bars and the like, nearly any desired graphic characters can be produced on dot-matrix printers, to a desired degree of resolution, given programmable and electronically stored character sets.
The resolution of characters or graphics in a dot-matrix printer is limited by the size of the smallest printable unit, such as a dot. Factors which are involved are the geometrical dimensions of the dot, and the maximum writing frequency at a given printing rate. The necessary provision of electronic storage is also a consideration. High resolution is required in order to obtain a good printout clarity, particularly in a case of characters that have slants or curves as a part of the character shape. A resolution which is too low can produce a step-shape representation of characters and symbols.
Dot-matrix printers are known which have means for printing dots along a line in a single column, in which are driven in a response to binary signals from a character generator. The character generator provides drivng signals which are delayed in successive lines. Such apparatus is described in German patent OS 2,457,884.
Slanted lines can be formed in the printed characters by means of a delay means. In U.S. Pat. No. 3,333,208, a serial dot-matrix printer is disclosed in which the actuation signals for the print elements can be delayed by different time periods, as a function of the desired slant of the character to be printed.